Abstract

In our study of carbon vapor molecules trapped in Ne matrices at 6 K, we observed laser induced fluorescencespectra of the system of upon excitation of the Mulliken transition of at 232 nm. A vibrational progression was clearly observed going from the upper vibrational level of the electronic D state into several lower levels of the state. We found that the progression spans from 359 to 517 nm with a large Franck–Condon shift showing the intensity maximum for the 0–2 or 0–3 transition. The vibrational constants for the state were derived as cm−1 and cm−1. We also observed the and the Swan band emissions, showing that from the excited D state also additional states were populated by internal conversion and intersystem crossing. The constants for the A state were derived as cm−1 and cm−1. Fluorescence excitation spectra of the vibronic transitions were found to reproduce well the relatively narrow absorption feature of the Mulliken system. We discuss the entirely different excitation spectra occurring in argon matrices in terms of matrix-site effects. Each vibronic band of the progression shows fine structures probably due to translations and librations of molecules coupled with the surrounding lattice of Ne atoms.